Sulphurization of esters



Patented July 14, 1942 T oss-ICE 1 SULPHURIZATION or its-mas Edwin Knowles and Frederic' 0. McCoy, BeacomN. Y, assignors, by mesne assignments, to The Texas Company, New York, N. Y., a corporation or Delaware l No Drawing.

Application September as, 1940,

Serial No. 358 877 7 Claims. (01. 260-399) This invention relates to a process of sulphuriz ing esters of unsaturated aliphatic acids that contain at least ten carbon atoms, The invention also. relates to new sulphurized products preparedirom the esters.

The products of the invention are intended primarily for use as additives to lubricating oils undersirable characteristics such as a tendency to cause corrosion. y

The esters which are employed as starting materials in the process of theinvention are simple esters of unsaturated aliphatic acidsthat contain at least ten carbon atoms. They include esters of unsaturated higher fatty acids and esters of aliphatic acids containing a ring structure. In esters of the latter type the aliphatic unsaturated linkage may appear in a ring. Thus, the term faliphatic. is used herein in its broad sense and includes cycloaliphatic as well as open chain compounds. In referring to simple esters it is meant thatthe esters contain but one ester group. The esters,'therefore, are distinguished from ordinary vegetable and animal oils, which are triesters of glycerine.

It has been found in accordance with the present invention that an ester of the above class can be converted into a sulphurized product containing a high proportion of sulphur and being characterized by a light color and excellent solubility in mineral oils by reacting the ester with sulphur at a temperature of at least 300 F. in the presence of water and under a pressure of hydrogen sulphide. The products resulting from this process are considerably lighter in color than products prepared from the same starting materials by ordinarysulphurizatlon processes using sulphur alone. The products make up a particularly valuable class of sulphurized materials as compared withmaterials obtained by the sullinolenic series.

are suitable, for use as starting materials in the a process. Theesters may be naturally occurring compounds or compounds prepared synthetically and may be substantially pure or containother compounds admixed therewith.v The esters may be esters of any of the familiar unsaturated fatty acids containing atleast ten carbon atoms, such as acids of the oleic series, linolic series, and Also the esters may be esters of unsaturated higher vfatty acids containing substituents such as hydroxyl. groups; e. g., the esters maybe esters of .ricinoleic acid. Where the esters are derived from, or may be regarded as derivatives of, unsaturatediatty acids it is preferred to employ esters of such acids which contain. from 16 to 18 carbon atoms, particularly oleic acid. As examplesof esters of aliphatic acids-containing a ring structure, there may be mentioned esters of abietic acid. The esterifying radicals of the esters may be unsubstituted or substituted aliphatic (including cycloaliphatic) or aromatic radicals. Inasmuch as the primary function of the estcrifying radical is believed to be the blocking of the carboxyl group in the acid, the specific nature of this radical is not of critical importance.' 'For example, where aliphatic; the

' esterifying radical may be saturated or unsaturated and may contain substituents such as amino and hydroxyl groups; e. g., this radical may be an allyl, a hydroxy-ethyl, or an. amino-ethyl radical. Valuable sulphurized products are obtainedfrom esters in which the esterifying radical is an open chain aliphatic radical such as a methyl, ethyl, propyl, octyl, or cetyl radical. ,Ad-

- ditional examples of suitable esterifying radicals are the cyclohexyl and phenyl radicals. Reprephurization of the usual vegetable andfanlmal oils because they are less viscous and more soluble in mineral oils. Since the sulphurized products do not contain undesirable free carboxylic acid radicals, they possess advantages over prod-.

'ucts resulting from the sulphurlzation of ,iree fatty acids.

From what has been said above, itlwill be sentative esters which may be employed as starting materials in the process are the following:

methyl oleate, ethyl oleate, cetyl oleate, methyl abietate," hydrogenated methyl abietate (containing one unsaturated linkage), and, the methyl ester of corn oil fatty acids. Sperm oil, which is largely cetyl oleate, yields a particularly valuable product when employed as the starting ma.- terial in the process' In carrying out the present process in accordance with a preferred manner of proceeding, sulphur, water, hydrogen sulphide, and an ester of the above class are introduced intoa reaction Vessel. Although the order in which these materials are introduced into the vessel may be varied, it is generally convenient to mix the ester, water, and sulphur either in the reaction vessel or before introducing them into the vessel,

recognized thatany of a large number of esters and th after closing V in roduce 2 the hydrogen sulphide through a suitable port. The reaction mixture is'heated to a temperature of at least 300 F? preferably between 320 and Thus, by maintaining the reaction mixone-half hour to two hours, the reaction is usually complete. I

At the completion of the reaction, the sulphurized product may be recovered in any suitable manner, the particular method employed depending primarily upon the specific character of the starting material. It is usually advisable first to cool the reaction mixture so as to prevent over-reaction. This may be done before releasing the pressure in the reaction vessel. One convenient method for recovering the sulphurized product isto mix the reaction mixture with a water insoluble solvent for the sulphurized product and then to permit the resulting mixture to stand and form two layers. The water layer is drawn oil and the solvent is removed from the sulphurized product by vaporization, preferably under reduced pressure conditions.

In this process it is important'to control several conditions if products of particularly valuable properties are to be obtained. As brought out in the following discussion, the partial pressure of hydrogen sulphide in the reaction vessel affects the properties of the products. This pressure preferably is not permitted to drop below 50 pounds per square inch and may be as high as 300 pounds per square inch or higherl It has also been foundthat the amount of water used has an important eilect upon the properties of the sulphurized products. Thus, if the water is used in an amount less than that corresponding to a weight ratio of water to ester of one to two, the color of the products is not as good as when the water is employed at least in this-amount. Although a greater quantity of water appears to have no adverse effect upon the properties of the products, apparently no improvement results and therefore a greater quantity ordinarily would not be used. In general, it may be stated that the weight ratio between the water and the ester should be maintained from 1:2 to 2:1.

Although the invention isnot limited to any theory of operation, it may be of advantage to point out that researches leading to the development of the invention have indicated that proceeding as above described prevents excessive polymerization due to linkage of double bonds.-

It appears that the dark color characteristic of ordinary sulphurized products is due at least in part to excessive polymerization of this type.

When sulphur alone is used in sulphurization,

. and 20 grams of'sulphur.

ent process may be carried out is an important factor in producing valuable sulfurized materials.

As will be apparent from a consideration of the following examples, as the temperature of thereaction mixture is raised the total pressure in the reaction vessel increases to a peak and then begins to decrease. Towards the end of the reaction, the pressure due to hydrogen sulphide is less thanat a prior period during the heating, indicating that the hydrogen sulphide not only dissolves in the reaction mixture under the pressure conditions, but also undergoes some reaction with the material being sulphurized. That a reaction occurs is also borne out'by the fact thatin many cases the sulphurized products contain more sulphur than the amount of free sulphur used would lead one toexpect.

As stated above the products prepared by the present process possess exceptional solubility in In order that the invention may be understood more fully reference should be had to the following examples in which are described typical ways of practising the present process It will be understood that these examples are given for illustrative purposes merely and are not intended as limitations of the invention.

Example I.-200 grams of winter-bleached sperm oil are agitated with 100 grams of water The resulting emulsion is poured into a reaction vessel having an internal volume of 600 cc. and'capable of withstanding substantial pressures. The reaction vessel is closed and 20 cc. of liquid hydrogen sulphide is introduced through a suitable port; then,

- the mixture.

tained at 320 to 330 F. for 45 minutes, at which time substantially no free sulphur remam in The reaction mixture is then cooled quickly by the action of cold water, the pressure in the vessel is released, and the reaction mixture is diluted with about an equal volume of methyl ethyl ketone. The resulting mixture is placed in a separatory funnel where a water layer and a layer composed of a methyl ethyl ketone solution form. .The water layer is drawn off and the methyl ethyl l retone solution is filtered. The solvent is removed from the solution under vacuum, and the product is finally stripped with steam under vacuum to remove the last traces of solvent and hydrogen sulphide.

In carrying out the above process the total pressure in the reaction vessel varies between about ,100 pounds and 350 pounds per square -inch. Thus, at all times during the reaction peried the partial pressure of hydrogen sulphide is substantially above 50 pounds per square inch.

Thejsulphurized oil resulting from this process is v a light-colored liquid which is excellently adapted for addition to lubricating oils of various types without discoloring the oils, as is the case when ordinary sulphurized products-"are added to -lubrlcating'oils. The sulphurized sperm oil conwins-110.5 per centjsulphunwhereas on thebasis of the free sulphur used the maximum amount theoretically possible is 9.1 per cent. This indicatesthat the hydrogen sulphide acts to introducesulphur'into'theproduct. r

Example 2.700' grams of winter-bleached sperm oil, 350' grams or water, 70 grams of sulphur, and 70 cc. o'i liquid'hydrogen sulphide are charged to a reaction vessel capable of withsel oi the type 'employed in Example '2'; Thereaction mixtureji is heat'ed to, 320 The reaction is -.carried out at a temperature ,above300 F: for a" periods: 'aboutw70 minutes; The ressure on the mixture reaches a'maSdmum of 327 pounds per square inch' and the final-pressure standing relatively high pressures and provided square inch. .At the end of this period the mixture, which contains substantially no free sulphur, i removed from the reaction vessel. The reaction vessel is washed out with methyl ethyl ketone, and the washings are added to the mixture. Additional methyl ethyl ketone is added to bring the total volume up to about. 1500 cc. An aqueous layer separates and is drawn off. The methyl ethyl ketone solution is filtered and vacuum steam stripped to remove the solvent. The stripped oil is filtered to yield a light strawcolored oil.

Example 3.The process of this example is similar to that 01' Example 2, except that the reaction mixture is'maintained at a temperature ranging from 300 to 320 F. for a period of 65 minutes.- Also, the pressure during this period .is =210- pounds per square inch; The reaction mixture is worked up as described in Example 2 to. yield a product :having agood color and being suitable for use as a lubricating oil or cutting oil additive. a It will be understood that the conditions described in the examples may be varied. -By substitutihg others of the class of esters herein defined, for example, those specificallyreferred to, for those employed in the examples, other valuable sulphurized products may be obtained. Generally, the amount of sulphur. employed is the same as that used in sulphurization carried outwith the use of sulphur alone. -Tosome' extent, however, the properties of the products may be varied in degree sulphur. a,

The timenecessary to complete the sulphurizetion reaction may be determined in any particular case by analyzing withdrawn samples of the reaction mixture to detect the presence of tree sulphur. when free sulphur is substantially abreaches a maximum ofabout .300 pounds per square. inch and at the end decreases to about 255 pounds per square inch. The reaction mixture is worked up as described in Example 2 to yield a similar product.

Example r-ThG process of this example is also similar to that of Example 2. However, the r,

sent in the reaction mixture, the reaction is com- .plete.. As statedv above, the reaction requires not more than two hours and may take as little as 30 minutes. Preferably the reaction is eflected in from '40 to 90 minutes. Although substa'n tial reaction-does not take place materially be? Where in the appended claims an ester of an aliphatic or fatty acid is referred toit will,

be understood that mixtures of such esters as well as compositions containing a substantial proportional one or more of such esters is intended unless otherwise indicated.

Since changes may be made, in ,the processes and products above described without departing from the scope of the invention, it will be understood that the above description is given for illustrative purposes merely and is not intended as a limitation of the invention.

We claim: v

'1. The process or manufacturing sulphurized products which comprises reacting a simplejester of an unsaturated aliphatic acid that contains at least ten carbon atoms with sulphur at a temperature of at least 300 F. in the presence of water and under a pressure of hydrogen sulphide. 2. The processor manufacturing sulphurized products which comprises maintaining at a temperature of at least 300 F. and under a pres-,

- sure or hydrogen sulphide a reaction mixture 2. The reaction mixture is heated to 320911,

the heating period at a temperature. over 300 F.being about minutes. The pressure on the mixture reaches a maximum of 227- pounds per square inch and the final pressure is 175 pounds per square inch. The sulphurized product is recovered as described in Example 2. The product contains 10.8 per cent total sulphur, color 'value (Tag Robinson) 9, and a Saybolt Universal viscosity of 40.5 at 210 F.

Example 6.--700 grams of Mazola (the methyl ester of corn oil fatty acids), 350 grams of water, 70 grams of sulphur, and 70 cc. of liquid hydrogen sulphide are charged to a reaction vesof hydrogen sulphide ofiat least 50 pounds per- I containing sulphur, water, and a simple ester of an unsaturated aliphatic acid'thatcontains at least ten carbon atoms, the weight ratio between the water and the said ester being at least 1:2, until substantially no-tree sulphur remains in the mixture, whereby said ester is converted into a sulphurized product having good color characteristics.

3. The process or manufacturing sulphurized products which comprises maintaining at a temperature of at least 300 F. and under a pressure square inch a reaction mixture containing lulby using varying amounts of phur, water, and a simple ester of an unsaturated aliphatic acid that contains at least ten carbon atoms,, the weight ratio between the a water and said ester being at least 1:2, until subproducts which comprises reacting a simple ester of an unsaturated fatty acid containing at least ten carbon atoms, the esterifying radical of said 1 gen sulphide of at least 50 inch.

ester being an open chain aliphatic radical, withv sulphur at. a temperature of at least 300 F. in the presence of water and under a pressure of hydrogen sulphide of at least 50 pounds per square inch.

chain aliphatic radical, the weight ratio between the water and said compound being at least 1:2, until substantially no free sulfur remains in the mixture, whereby said ester is converted into a sulphurized product having good color characteristics.

6. The process of manufacturing sulphurized products which comprises reacting sperm oil with sulphur at a temperature of at least 300 F. in the presence of water and under a pressure of hydropounds per square 7. The process of manufacturing sulphurized products which comprises maintaining at a temperature of at last 300 1". and under a pressure of hydrogen sulphide of at least pounds per square inch a reaction mixture containing sperm oil, sulphur. and water, the weight ratio between the water and the sperm oil being at least 1:2, until substantially no free sulphur re-- mains in the mixture. whereby the sperm oil is converted into a sulphurized product having good color characteristics.

EDWIN C. KNOWLES. FREDERIC C. MCCOY. 

